The major goal of this research is to investigate the regular structures that result from the self-assembly of deoxy-HbS molecules. Knowledge of the molecular organization would enable determination of intermolecular contacts that stabilize the structures. Prevention or interruption of their formation would constitute a means of eliminating sickle cell disease. Attempts to describe the structure, derived from X-ray diffraction data, of the deoxy-sickle hemoglobin fiber at near-atomic resolution have resulted in multiple, closely related fiber models. A search for a unique structure, and a subsequent refinement of that structure will be undertaken with newly acquired higher resolution diffraction data. Other regular structures of deoxy-HbS that have not been previously reported are magnetically induced. They have been observed in the electron microscope when the starting deoxy-HbS solution was considerably below its saturation concentration. The physico- chemical properties over a range of concentrations of deoxy-HbS solutions in a magnetic field will be investigated by modified standard methods. This should yield information for improving sample preparations in order to enhance the resolution of the electron micrographs from which the molecular structure of these arrays may be determined by reconstruction of electron micrographs from which the molecular structure of these arrays may be determined by reconstruction of electron microscope images and/or by electron diffraction. A somewhat different approach in the prevention of fiber formation, other than the design of stereo-specific antisickling agents, is the investigation of the nuclei from which fibers form in a concerted manner. Information about the size, shape, and number of nuclei prior to fiber formation could result in a means of interrupting the succession of events that lead to almost instantaneous deoxy-HbS gelation in erythrocytes. An investigation of the morphology of the nuclei will be undertaken by studies of their small angle X-ray scattering. With the advent of the Advanced Photon Source, within the next few years, it may even be possible to study the time course of nuclei to fiber formation. the structure of deoxy-HbS aggregates, whether they be the fibers so extensively studied, or the new structures we have observed, will be investigated through techniques of X-ray diffraction and electron microscopy. Such information may lead to the ultimate goal, the alleviation of sickle cell disease.